1. Field of Invention
This invention relates to a method of welding metal components using a laser beam and more particularly to welding such components with a laser beam without prior surface cleaning or edge preparation.
2. Background Information
In conventional welding processes, such a gas-metal-arc welding (CMAW), gas-tungsten-arc-welding (GTAW) are flash welding (FW), existing practice is to utilize cleaned surfaces, frequently accompanied by special end preparations machined on the mating surfaces of the parts to be welded. Cleaning of the surfaces to be welded is necessary, principally, because the natural oxides present on the surfaces tend to inhibit wetting. Additionally, they may contribute to weld metal contamination forming porosity and cracks thus resulting in the production of inferior quality weldments with corresponding lower mechanical properties. Likewise, the efficient welding of many components may necessitate expensive and time consuming machining operations to produce the required edge preparation on the parts prior to the welding process.
These welding processes also require feeding metal filler wire into the weld to build up the weldment. Conventionally, electrical continuity must be established through the feed wire to melt it. A recently developed feed drive described in U.S. Pat. No. 4,447,703 resistively heats the filler wire prior to its entry into the weld pool.
Lasers are now being used to weld metal components, however, it is still the practice to clean the surfaces to be joined and prepare the edges in the same manner as with the other prior art welding methods.
In one form of laser welding used on heavy sections called keyhole welding, the beam is sharply focused to increase energy density and create a hole or cavity surrounded by liquid metal in the base metal which moves along with the laser beam as the parts are joined in one pass. A good fit between the parts to be joined has been considered a prerequisite for such keyhole welding which requires in many instances edge preparation to assure good contact of the surfaces to be joined. This is done in addition to thorough cleaning of the surfaces to remove contamination prior to welding. In conduction laser welding a less focused beam is used with filler wire. Again, it has been considered necessary to remove surface contaminants prior to welding.
In many applications, parts to be joined by welding are covered with oxides, mill scale, grease or paint et cetera. It is time consuming to remove these contaminants before welding, but to date it has been considered a necessary step in achieving a quality weld. Edge preparation is also time consuming and expensive, but has also been considered a prerequisite to producing a good weld.
It is a primary object of the invention to provide a method of welding metal components which does not require surface cleaning or edge preparation.